A very important parameter when splicing optical fibers by welding is the temperature at the welding location. To be able to maintain the temperature of the fibers at a sufficiently high level and during a sufficient long time period are determining factors in order to obtain a low attenuation and a high mechanic strength in the splice produced.
A known method for an indirect control of the temperature of the fibers, which is used in some known welding devices, is called "Meltback", see the article by G. Kiss, "High yield fusion splicing in the outside plant: using fiber meltback to monitor electrode condition", National Fiber Operation Engineering Conference, Denver, USA, September 1996.
In Patent Abstracts of Japan, abstract of the Japanese patent application No. 2129607, a fusion splicing device is disclosed, in which the brightness of an optical fiber heated in an arc discharge is observed. The discharge heating temperature is checked from the area of the bright part of the optical fiber.
When optical fibers assembled to optical fiber ribbons are to be spliced by melting the ends of the optical fibers in an electric arc, a problem exists of making the ends of the opposite individual fibers contact each other before and/or in the very fusioning process. This is due to the fact that it is very difficult to cut off such fiber ribbons at an exactly straight angle in relation to the longitudinal direction of the respective fiber ribbon. Also, the operation of stripping the polymer protective coating of a fiber ribbon and the force then used can result in that some fibers in a fiber ribbon will be elongated more than other fibers. Hence, the end surfaces will of the fiber ribbon will not even be located in a plane.
In Patent Abstracts of Japan, abstract of the Japanese patent application No. 5-142442, a fusion splicing method for "multiple fibers" is disclosed, in which the connecting ends of optical fibers are preheated "at a low temperature to the extent of not attaining an excess molten state. The molten end faces of the optical fibers are then pressed to each other and while the end faces are heated in the state at the temp. higher than the above-mentioned preheating temp., the optical fibers are pushed in, by which the optical fibers are fusion spliced."